periodically by hurricanes in subsequent years and portions of the highway 

 have been rebuilt landward. The most recent maintenance took place during 

 early 1988, when concrete -filled bags and boulders were used to stabilize the 

 revetment to the west of the breakwater system constructed in January, 1986. 

 The eastern end of the revetment was reinforced in a similar manner with a 

 combination of mats of concrete blocks and boulders. This additional attempt 

 at stabilization was necessary because the highway presently fronts lower 

 elevation back marshes and cannot be relocated landward without considerable 

 coast. 



The breakwater system consisting of six segments represents a significant 

 departure from a revetment as a shore protection measure. Although originally 

 conceived as a T-groin system, this project was modified to a series of 

 segmented detached breakwaters consisting of various quantities and arrange- 

 ments of timber piles, used tires, and riprap, which provided different 

 amounts of wave transmission (Fig. 8). By allowing some degree of wave 

 transmission, the longshore movement of sand would not be completely inter- 

 rupted at the breakwaters, and downdrift erosion of the natural shoreline 

 would be reduced. The breakwaters were constructed as a prototype test of a 

 low-cost shore protection method with the multiple objectives of preserving 

 and possibly widening the narrow beach, protecting the revetment, and reducing 

 wave overtopping and flooding of the highway. The concern for downdrift 

 beaches in addition to the critical eroding area at the breakwater site is an 

 example of comprehensive shore protection project planning as discussed by 

 Kraus (1989). 



The Louisiana Geological Survey (LGS) and the Coastal Engineering Research 

 Center (CERC) , U.S. Army Engineer Waterway Experiment Station, initiated a 

 monitoring program consisting of periodic vertical aerial photography, 

 quarterly beach profile surveys, and visual observation of local waves and 

 nearshore circulation. This included pre-project aerial photography and 

 surveys to establish preproject conditions. Nakashima et al . (1987) qualita- 

 tively evaluated the breakwaters to have approximately increasing transmis- 

 sivity from west to east, with the rock riprap breakwater at the west end 

 allowing the least transmission and the breakwater at the east end (tires 



52 



